不同干燥方式对藕片品质的影响

Effects of different drying methods on the quality of lotus root slices

目的探究不同干燥方式对藕片品质的影响。方法测定不同热风干燥温度下不同厚度藕片的干燥曲线,并表征其水分迁移特征,以真空冷冻干燥为对照,比较不同干制条件下藕片理化特性(外观、褐变度、色泽、收缩率)和营养品质[维生素C(vitamin C,VC)、总黄酮、总酚含量]的差异。结果热风干燥过程中,藕片干燥速率随温度升高、厚度减小而增大,其中,干燥温度为50℃时,藕片无法干燥至安全水分范围(干基含水量≤15%),60℃、70℃温度下,不同厚度藕片最终含水量均可降至安全水分范围;水分迁移特征显示藕片干制过程中干燥前期游离水蒸发,固定水和束缚水比例增加,最终干制藕片中水分主要以束缚水形式存在;不同热风干燥条件对比之下,温度为60℃、厚度10mm、保留水分15%时,干制藕片色泽较好、褐变和收缩率最低,总黄酮含量、总酚含量及VC保留量较高,营养保留程度与真空冷冻处理得到的藕片营养品质接近,干制效果优于其他干燥条件。结论从藕片理化性质、营养品质及干燥效率等相关方面考虑,热风干燥温度为60℃,切片厚度为10 mm,保留水分15%左右,干燥时长大约在280 min左右时,藕片理化特性和营养品质得到最大程度保留,因此可作为藕片干制的推荐方式。

Objective To explore the effects of different drying methods on the quality of lotus root slices.Methods The drying curves and water migration processes of lotus root slices with different thicknesses dried at different hot air temperatures were determined,and their physicochemical properties(surface morphology,browning degree,color,shrinkage)and nutritional quality[vitamin C(VC),total flavonoids,total phenol content]were compared,with lotus root slices dried by vacuum freeze as the control.Results During the hot air drying process,the drying rate of lotus root slices increased with the increase of temperature and decrease of thickness,among which the lotus root slices could not be dried to the safe moisture range(dry base water content≤15%)at 50°C,while the final water content of different thicknesses of lotus root slices could be reduced to the safe moisture range at 60°C and 70°C.The water migration characteristics of lotus root slices showed that free water evaporated in the early drying stage,and the proportion of fixed water and bound water increased,finally the water in the dried lotus root slices mainly existed in the form of bound water.Under different hot air drying conditions,lotus root slices dried at 60°C with the thickness of 10 mm and moisture retention of 15%,had better color,the lowest browning and shrinkage rate,and higher total flavonoid,total phenol content and VC retention than other drying conditions.The nutrient retention degree of the lotus root slices at this drying condition was close to that obtained by vacuum freeze drying.Conclusion Taking consideration of physical and chemical properties,nutrition and drying efficiency of lotus root slices,the properties and nutritional quality of lotus root slices dried at 60°C,a slicing thickness of 10 mm,a moisture retention of about 15%and a drying time of about 280 min to the greatest extent,so that this hot air drying condition can be a recommended way for lotus root drying.